1. Field of the Invention
The present invention relates to a drug delivery granule, more particularly, a drug delivery granule capable of slowly releasing impregnated drug components therefrom. Since the drug delivery granule of the present invention has a controllable and good prolonged effect of the drug release and a good imaging property to an X-ray or ultrasonic wave, it can be advantageously used in fields such as chemotherapy. The present invention also relates to a process for the production of such a drug delivery granule.
2. Description of the Prior Art
In the field of a chemotherapy, it has been desirable to provide slow release drugs which can exhibit a prolonged effect or action thereof for the longest possible period. In particular, since transvascular chemotherapy has recently been developed, and is effectively used to treat hepatoma or similar tumors, researchers are studying slow release drugs which are effective for transvascular chemotherapy.
For use in chemotherapy, several types of slow release drugs are well-known. Typical examples of prior art slow release drugs include a sponge preparation comprising sponge-like particles of the substance originated from an organism, such as gelatin or the like, and a drug component impregnated in the particles, or a suspension of drug particles in a fatty oil such as LIPIODOL (trade name of an ethyl ester of iodized poppy seed oil fatty acid; commercially available from Kodama K. K.). However, these drug particles suffer from many drawbacks such that the drug is not concentrated on a site to be treated due to uneveness of the size of the particles; that the length of the effect of the drug is not satisfactory because the drug is easily diffused in and absorbed by a living body; and that, after application, the drug can not be traced because it has no imaging property to the X-ray or ultrasonic wave.
Further, Japanese Unexamined Patent Publication (Kokai) No. 60-106459 discloses that a calcium phosphate-based filler containing an antibiotic substance can be produced by coating beads of a combustible substance with calcium phosphate, piercing the coated beads to open small holes therein, firing the beads to remove the combustible substance and filling the obtained hollow beads with the antibiotic substance through the hole of the bead wall. After filling of the antibiotic substance, the hole is closed or sealed to produce an antibiotic substance-containing filler. However, this production method is not suited for producing small size fillers, because it is essential to open a small hole in the bead wall. Only relatively larger fillers having a diameter of 2 to 40 mm can be produced. In addition, it requires troublesome operations such as filling of the antibiotic substance or sealing of the holes.